Gyanu joined Congress in the presence of Bihar PCC president Ashok Chaudhary signalling a dispute within RJD after the imprisonment of Prasad.
Welcoming him to Congress, Chaudhary said Gyanu would strengthen party base in Patna where Congress does not have a strong base.
He said Gyanu joining the party would draw youths to it.
Gyanu, who was accompanied by a large number of supporters to the Congress state headquarters Sadaquat Ashram, said he joined the party as he was impressed with the vision and approach of its Vice-president Rahul Gandhi for the youth and the country.